adsabs/AstroCLIMB huggingface dataset:
Paper: The Star Formation Rate of the Milky Way as Seen by Herschel
Authors: D. Elia, S. Molinari, E. Schisano, J. D. Soler, M. Merello, D. Russeil, M. Veneziani, A. Zavagno, A. Noriega-Crespo, L. Olmi, M. Benedettini, P. Hennebelle, R. S. Klessen, S. Leurini, R. Paladini, S. Pezzuto, A. Traficante, D. J. Eden, P. G. Martin, M. Sormani, A. Coletta, T. Colman, R. Plume, Y. Maruccia, C. Mininni, S. J. Liu
Figure caption: Left: the same as in Figure 7, but with atomic gas surface density on the x-axis (from Nakanishi & Sofue 2016), instead of the molecular one. The KS relation is also plotted as a dashed line. Right: the same as in Figure 7 and in the left panel of this figure, but with total gas surface density on the x-axis. In both panels the x-axis range has been kept identical to that of Figure 7, to facilitate comparison.
Paper: The Star Formation Rate of the Milky Way as Seen by Herschel
Authors: D. Elia, S. Molinari, E. Schisano, J. D. Soler, M. Merello, D. Russeil, M. Veneziani, A. Zavagno, A. Noriega-Crespo, L. Olmi, M. Benedettini, P. Hennebelle, R. S. Klessen, S. Leurini, R. Paladini, S. Pezzuto, A. Traficante, D. J. Eden, P. G. Martin, M. Sormani, A. Coletta, T. Colman, R. Plume, Y. Maruccia, C. Mininni, S. J. Liu
Figure caption: Cumulative SFR profile as a function of the heliocentric distance. Since the distance d appears as an upper limit of integration, here the integration variable is called s.
Paper: Uncertainty and Bias of Cosmology and Astrophysical Population Model from Statistical Dark Sirens
Authors: Hang Yu, Brian Seymour, Yijun Wang, Yanbei Chen
Figure caption: Bias on h due to an error in the astrophysical rate Δr given by Equations (25)–(27). An error in m 1 but constant in redshift can then be obtained by summing over all the pixels along a specific μ  m,err (i.e., a vertical line) with appropriate normalization. Likewise, other generic Δr can be obtained by summing over the corresponding pixels. Also shown with the dotted brown line is an approximation of the detection threshold with ﹩{\left[{{ \mathcal M }}_{c}(1+z)\right]}^{5/6}/z\simeq \mathrm{constant}﹩.
Paper: Uncertainty and Bias of Cosmology and Astrophysical Population Model from Statistical Dark Sirens
Authors: Hang Yu, Brian Seymour, Yijun Wang, Yanbei Chen
Figure caption: Error ellipses for a sample of 40 BBH events similar to the GWTC-3 catalog. The gray ellipses are obtained by summing the Fisher information from the marginalized redshift and primary mass distribution together, and the olive ones are from the 3D r(m 1, m 2, z) distribution.
Paper: Uncertainty and Bias of Cosmology and Astrophysical Population Model from Statistical Dark Sirens
Authors: Hang Yu, Brian Seymour, Yijun Wang, Yanbei Chen
Figure caption: Correlation between astrophysical and cosmological parameters by inverting a 3 × 3 Fisher matrix including (h, μ  g , R) (top panel) or (h, γ, R) (bottom panel). The cyan ellipses correspond to constraints from the redshift distribution alone (cf. Figure 1). As μ  g  and/or γ decreases, h will increase to a greater value. It captures the key features shown in Figure 10 in LIGO Scientific Collaboration et al. (2021d). If one further incorporates the information from the mass distribution (orange ellipses; cf. Figure 2), the combined uncertainties can be reduced to the gray ellipses.
Paper: Uncertainty and Bias of Cosmology and Astrophysical Population Model from Statistical Dark Sirens
Authors: Hang Yu, Brian Seymour, Yijun Wang, Yanbei Chen
Figure caption: Error ellipses from the 3D r(m 1, m 2, z) distribution assuming 500 BBH events using the model in Fishbach et al. (2018). Our results show good agreement with those obtained in Fishbach et al. (2018) and Farr et al. (2019). It thus validates our approach when n obs is large.
Paper: Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques
Authors: Ruizhu Chen, Junwei Zhao, Shea Hess Webber, Yang Liu, J. Todd Hoeksema, Marc L. DeRosa
Figure caption: Comparison of near-side and far-side images taken at or near 00:00 UT on 2014 March 13. (a) SDO/AIA-observed near-side 304 Å image; (b) STEREO/EUVI-observed far-side 304 Å image after merging observations from both STEREO-A and STEREO-B spacecraft. (c) SDO/HMI-observed near-side magnetic field; and (d) time–distance helioseismic far-side image obtained from the SDO/HMI-observed near-side Dopplergrams. The magnetic field is displayed with a scale of −200 to 200 G, the helioseismic image is displayed with a scale of phase shifts from −0.10 to 0.10, and the EUV images are displayed with a data number from 10 to 2000. The STEREO/EUVI 304 Å image is displayed after its intensity is calibrated to match the SDO/AIA 304 Å level.
Paper: Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques
Authors: Ruizhu Chen, Junwei Zhao, Shea Hess Webber, Yang Liu, J. Todd Hoeksema, Marc L. DeRosa
Figure caption: Flowchart showing the entire procedure of making far-side magnetic-flux maps using the near-side Doppler-velocity observations. Yellow boxes represent original data inputs, green boxes represent intermediate data products, and the red box represents our final data product. Purple diamonds represent the methods that are used in the corresponding processes.
Paper: Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques
Authors: Ruizhu Chen, Junwei Zhao, Shea Hess Webber, Yang Liu, J. Todd Hoeksema, Marc L. DeRosa
Figure caption: Comparison of mean SDO/AIA 304 Å flux and mean SDO/HMI line-of-sight magnetic flux density, after degradation of the SDO/AIA 304 Å data is recalibrated.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: Scaling of prominence and density of spectral lines. Top: number of lines vs. effective temperature for PHOENIX models truncated to IGRINS (blue connected points) and HPF (red free-standing points) bandwidths, for different prominence thresholds of 0.02, 0.01, and 0.005. Bottom: number of lines per 100 Å wavelength bin for stellar (blue, upper envelope of steps) and telluric (orange, lower envelope of steps), illustrated for a T eff = 4700 K, ﹩\mathrm{log}g=4.5﹩ PHOENIX model and a T = 290 K, relative humidity of 40% TelFit model.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: Visual flowchart of the blasé forward model. Step 0 (not shown) is to choose a precomputed synthetic stellar spectrum—and, optionally, a precomputed synthetic telluric spectrum—with physical properties close to the target and observing conditions. Both the stellar and telluric spectra get cloned (Step 1). The stellar model is warped to its extrinsic properties (Step 2), and then the stellar and telluric models get multiplied together (Step 3). Next, this joint model is convolved with an instrumental kernel and resampled to the wavelength coordinates of the data spectrum (Step 4). It is this forward model that gets directly compared to the observed spectrum (not shown).
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: PHOENIX spectrum cloned with blasé. This T eff = 4700  K, ﹩\mathrm{log}g=4.5﹩ solar-metallicity model has 9028 individual cloned spectral lines, each with three tuned parameters. The pictured 50 Å chunk contains 121 spectral lines and represents about 1% of the entire spectral bandwidth that was cloned. Some flaws can be seen near the cores of deep lines or wings of broad lines.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: Zoom-in of the region between the vertical gray bars in Figure 3. The cloned model has seven spectral lines describing the 400 pixels in this 4 Å chunk. The native PHOENIX pixel sampling can be seen as the boxy steps in both the native and cloned models.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: Precomputed TelFit model cloned with blase. Before: the top panel shows a forward model evaluated with coarsely initialized line-by-line properties, based on simple threshold-based peak finding and crude estimation of the shape of the line. After: the bottom panel shows the blase fine-tuned clone, with nearly identical spectral structure.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: WASP 69 observed with HPF, compared to a T eff = 4700  K, ﹩\mathrm{log}g=4.5﹩ solar-metallicity PHOENIX model warped to ﹩v\sin i=2.2﹩ km s−1, RV = −9.6 km s−1, and HPF resolving power.
Paper: Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques
Authors: Ruizhu Chen, Junwei Zhao, Shea Hess Webber, Yang Liu, J. Todd Hoeksema, Marc L. DeRosa
Figure caption: Scatter plot comparing the mean magnetic-flux densities from the STEREO-generated maps with those from the helioseismic-image-converted maps, both of which are from the test data set.
Paper: An Interpretable Machine-learning Framework for Modeling High-resolution Spectroscopic Data 
Authors: Michael Gully-Santiago, Caroline V. Morley
Figure caption: Semiempirical model of WASP 69 transfer-learned with blase, employing a regularization prior on the learned amplitudes.
Paper: Multiwavelength Observations of MWC 297: Constraints on Disk Inclination and Mass Outflow
Authors: William D. Vacca, Göran Sandell
Figure caption: (a) Observed and (b) dereddened SED of MWC 297. Red points denote the values derived from SOFIA/FORCAST, while blue points are from Herschel/PACS and SPIRE, and green points are from newly measured submillimeter/radio observations. Pink diamonds represent values taken from the literature. Blue diamonds are literature values that were not considered in the fit or were combined to generate values shown in pink. Vertical dashed lines connect values for the core and the extended region. The solid black line is the IRTF/SpeX spectrum and the solid green line is the ISO spectrum. The solid dark blue line is a Kurucz model for a B1.5V star, reddened by A  V  = 8.1 mag in (a).
Paper: Multiwavelength Observations of MWC 297: Constraints on Disk Inclination and Mass Outflow
Authors: William D. Vacca, Göran Sandell
Figure caption: Least squares fit to the radio and 3 mm flux densities of MWC 297, which yields a spectral index α ∼ 1.03. Data points plotted with circles were omitted from the fit. The 850 and 450 μm flux densities are from Sandell et al. (2011), while the 160 and 100 μm PACS data are from this paper. The dotted–dashed line shows an extension of the fit to shorter wavelengths. There is a clear excess of flux (above the extension to the fit) at 100 and 160 μm, continuing down to about 450 μm. The turnover frequency appears to be between 850 and 450 μm. The dashed line shows the case when the wind becomes optically thin at 400 GHz (750 μm). Values above the dashed line are due to emission from warm dust.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Example SED fits in each category of χ 2: good (top), decent (middle), and poor (lower). The data are shown as black points. The median fit stellar (pink), stellar+dust (purple), and stellar+dust+bias (cyan) are overplotted. The subpanels show the residuals in units of σ. The top panel shows all residuals of the best model (cyan) within 4σ. The middle panel shows residuals of the best model (cyan) within 12σ (note that for five bands, the value is closer to 4σ). The bottom panel shows the largest deviations in the residual with the best model (cyan) being within 15σ. For the good and decent fit, we report ﹩\mathrm{log}({T}_{\mathrm{eff}})﹩, ﹩\mathrm{log}(g)﹩, and A V.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Keck/LRIS and MMT/Binospec normalized spectra (with an arbitrary offset added for clarity) for all 18 stars in the spectroscopic sample. For stars with both Keck and MMT data, we show the Keck spectra in the 4000–5100 Å region. If there is no LRIS spectrum, we show the Binospec (1000 lpmm) spectrum. The spectra in the 6520–6610 Å region are from the Binospec 270 lpmm grating and are shown for all stars that have Binospec spectra. The spectra are sorted by spectral type from O-type stars at the top to B-type and Be-type stars at the bottom. This is one of the largest set of optical spectra for sub-SMC metallicity massive dwarf stars.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Comparison between the parameters derived for K1 using full spectral fitting and SED fitting. We show a plot of the observed spectra (black dots), the TLUSTY-based model generated by the median parameters derived from the full spectral fitting (pink), and the TLUSTY-based model generated by the median parameters derived from the SED fitting (blue). While both models reasonably replicate the observed He I 4471 and He II 4541 fits, both struggle to fully fill the absorption feature of the helium lines. This shortcoming is potentially due to the fixed resolution, metallicity, or macroturbulence. We see the effect of the different ﹩\mathrm{log}(g)﹩ values between the methods most prominently in the Balmer lines (see the Hβ feature). The gray bar shows the part of the spectrum that we masked.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: A panchromatic gallery of CMDs for Leo A ranging from UV-optical on the left to NIR on the right. Points in each row are color-coded by results from SED fitting with the BEAST. From top to bottom, the rows reflect: χ 2, ﹩\mathrm{log}({T}_{\mathrm{eff}})﹩, ﹩\mathrm{log}(g)﹩, M ini, and A V. For χ 2, we divide the fits into three categories: good (pink), decent (purple), and poor (cyan). Stars that have spectroscopic data are plotted as squares.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Top panel: the Leo A HST ACS/F475W image zoomed in on two H II regions. Stars with spectroscopic observations are labeled by their reference names. Contours of Hα emission from ground-based imaging are overplotted in green. The H II regions are overplotted with the stars color-coded by log(Age) <7.5 dex from the BEAST fits and include only good fits from the UV-optical catalog. Bottom panel: the optical CMDs are overplotted with the stars shown in the top panel and use the same color-coding for both regions.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: A comparison between the parameters derived from the BEAST using the models with v/vcrit = 0.4 (PHOT) and the parameters derived from the PAYNE (SPEC). The top panel compares ﹩\mathrm{log}({T}_{\mathrm{eff}})﹩. The middle panel compares ﹩\mathrm{log}(L/{L}_{\odot })﹩. The bottom panel compares ﹩\mathrm{log}(g)﹩. The comparison between the two methods shows that panchromatic photometry can be used to recover reliable stellar parameters at least for “normal” single stars.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: UV-optical (left) and optical (right) HST-based CMDs of Leo A. The pink colored circles are stars that appear in the BHeB region both in the UV and the optical CMD. The blue colored circles are stars that are on the MS in the UV CMD, but appear on or near the BHeB region in the optical CMD. The cyan squares are the stars identified as Be stars in our spectroscopic sample. This shows candidate Be stars could possibly pollute the BHeB in the optical CMD, and that we can filter for candidate Be stars in panchromatic photometry studies.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: The distribution of radial velocities for stars in Leo A. Our LRIS (blue) and Binospec (pink) velocities are consistent with the Keck/DEIMOS-based velocities of red giants (RG) measured by Kirby et al. (2017), and the average velocity measured from the Supergiants (SG) by Brown et al. (2007). Each sample is normalized by counts.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Models for K6 from adapted composite SED fitting (see Section 4.3). The data (black dots) are matched by scaling and combining the stellar models. The star (blue line) and the disk (red line) are combined for the composite SED (black line). The stellar and the disk models are both varied to find the median SED. We note that the error bars of the data are smaller than the dots representing the data point.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Corner plot of stellar parameters from the adapted double SED fitting of K6. The first two columns show the contours for the derived ﹩\mathrm{log}({T}_{\mathrm{eff}})﹩ and radius of the star. The next two columns show the contours for the derived ﹩\mathrm{log}({T}_{\mathrm{eff}})﹩ and radius of the disk. The last column shows E(B − V).
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: Three panels comparing the different masses derived throughout the study: M ini and M act from the photometry, M 0, M evo, and M spec from the spectroscopy. The top-left panel compares the initial masses derived from each method (M ini vs. M 0). The top-right panel compares the present-day masses derived from each method using evolutionary tracks and isochrones (M act vs. M evo). The bottom panel compares the present-day masses derived from spectroscopy (M spec vs. M evo). We show all stars with χ 2 < 100 in both photometry and spectroscopy.
Paper: A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A 
Authors: Maude Gull, Daniel R. Weisz, Peter Senchyna, Nathan R. Sandford, Yumi Choi, Anna F. McLeod, Kareem El-Badry, Ylva Götberg, Karoline M. Gilbert, Martha Boyer, Julianne J. Dalcanton, Puragra GuhaThakurta, Steven Goldman, Paola Marigo, Kristen B. W. McQuinn, Giada Pastorelli, Daniel P. Stark, Evan Skillman, Yuan-sen Ting, Benjamin F. Williams
Figure caption: The HR diagrams of massive sub-SMC metallicity stars in the Local Group with derived stellar parameters. We overplot MIST tracks. Top: all of the stars with temperatures and luminosities in the metal-poor galaxies: WLM (∼15% Z⊙; aqua triangle), IC 1613 (∼14% Z⊙; blue circles), and NGC 3109 (∼11% Z⊙; purple-blue squares). The WLM stars are from Bresolin et al. (2006), Tramper et al. (2011, 2014), and Telford et al. (2021b); the IC 1613 stars are from Bresolin et al. (2007), and the NGC 3109 stars are from Evans et al. (2007), Tramper et al. (2014), and Hosek et al. (2014). Bottom: all stars with temperatures and luminosities in the extremely metal-poor galaxies Sextans A (∼6% Z⊙; purple triangle) and Leo P (∼3% Z⊙; rose squares). As well as the stars in our spectroscopic sample (∼5% Z⊙; pink circles). The Sextans A stars are from Kaufer et al. (2004), Camacho et al. (2016), and Telford et al. (2021b); the Leo P star is from Telford et al. (2021b). Our sample represents the first extended sample of MS stars at sub-SMC metallicities with derived stellar parameters. Furthermore it is the largest sample at sub-10% Z⊙ with derived stellar parameters.